Developing an Implementation Strategy for Post-concussion Communication With Low Health Literacy Parents in the Emergency Department: Complete Statistical Analysis

1. Trial at a Glance

This page covers the registry results for Developing an Implementation Strategy for Post-concussion Communication With Low Health Literacy Parents in the Emergency Department (NCT04112914), a randomized na study. The primary outcome is Change in Concussion Management Behaviors: Communication.

2. Clinical Question

3. Trial Design

This was a randomized study of a behavioral educational intervention for families receiving emergency-department care for concussion. The registry record identifies the allocation as randomized, masking as none, and the model as sequential. The record does not describe the sequence in further detail, so the precise implementation of the sequential model is not reported in the registry record.

The intervention was called Post-concussion education for families. One group received the newly developed education; the comparison group received education and healthcare-provider communication as usual during the emergency-department visit. The study was sponsored by Seattle Children’s Hospital and had an enrollment of 98. Its status is completed. The recorded study start was 2021-01-05, and primary completion was 2022-07-27.

The investigators described the project as a hybrid implementation-effectiveness evaluation. Its primary outcome was parent self-report of specific concussion management behaviors two weeks after the visit. The stated additional interests were whether successful implementation was associated with parent knowledge and self-efficacy related to helping a child follow CDC guidance for returning to daily activities, school, and sports, and whether knowledge and self-efficacy disparities between parents with high and low health literacy decreased.

The registry record lists seven outcome measures and seven analyses. It names four secondary outcomes: changes in self-efficacy for communication, supportive or rehabilitation-related behaviors, and follow-up, and change in concussion knowledge. Further details about the sequence of study stages, allocation procedures, recruitment, or the study’s original design assumptions are not reported in the registry record.

4. Participant Flow and Accounting

The registry reports how participants moved through each stage of the study. All counts below are exactly as posted; missing counts are not inferred from other stages.

Before assignment: N/a. All enrolled participants were assigned to the control or intervention condition.

Overall Study

Reasons for not completing this period:

Analysis population for the primary outcome, as defined in the registry: All participants who responded to concussion management behavior items two weeks post-visit \[Cohorts 1 and 2.

5. Baseline Characteristics

The table reproduces the baseline characteristics posted in the registry, which describe the participants analysed at baseline and help show whether the randomized groups were comparable.

6. Primary Endpoint

The registry lists the primary outcome as Change in Concussion Management Behaviors: Communication, measured over Timepoint 3 [Two weeks post-visit].

The primary endpoint is the mean score on the Concussion Management Behaviors: Communication measure at Timepoint 3, two weeks after the visit. Parents reported whether they had used three emotionally supportive communication practices with their child: discussing how the child was feeling emotionally, explaining that recovery time can differ from person to person, and discussing concerns about recovery from head injury. The responses were summed into an index with a possible range of 3 to 9. Higher scores indicate more supportive communication during recovery.

This measure was used to capture a specific, parent-reported behavior in the home setting after the emergency-department visit. It therefore addresses an intended aspect of communication support, rather than a clinical outcome or a direct measure of the child’s recovery. The registry record reports Cronbach’s alpha=0.59 for the index. This is a measure of internal consistency, and its value is relevant when interpreting how consistently the items function together as a scale. It does not, by itself, establish that the measure captures every relevant aspect of supportive communication.

The outcome description calls the endpoint a change in communication behaviors, but the posted arm summaries give mean scores at the two-week timepoint. The registry analysis is described as a mean difference in final values. A baseline-adjusted change estimate is not reported in the registry record.

7. Results Posted in the Registry

• New Education: mean 6.71 versus 5.49 on control; difference 1.22 (95% CI 0.08 to 2.36), standardized effect d = 0.70; z-test p = 0.036.

8. Statistical Interpretation

9. Statistical Methods Explained

The primary outcome is continuous: it is a score on a scale, summarized by a mean and standard deviation. A mean difference expresses the separation between the two group averages in the original score units. In the unadjusted recalculation, the group means are 5.49 for Education as Usual and 6.71 for New Education, and the mean difference is 1.22 points. This uses the observed score scale directly, which makes the estimate interpretable in terms of the communication index.

The posted summary statistics also report standard deviations of 1.68 and 2.02. A standard deviation describes how dispersed individual scores are around their group mean. It is not the uncertainty of the mean itself: the standard error is a measure of uncertainty in an estimated mean, and the reported standard errors are 0.215 and 0.540. General statistical explanation: uncertainty in a group mean depends on both the variability of individual measurements and the number of observations contributing to that mean. A smaller group can therefore yield a less precise mean even when its observed variability is similar.

The recalculated comparison is an unadjusted comparison of posted summary statistics. It gives a mean difference of 1.22, a 95% confidence interval from 0.081 to 2.359, and p=0.036. General statistical explanation: a confidence interval describes a range of effect estimates compatible with the data under the calculation’s assumptions. A p-value measures how unusual the observed result, or a more extreme one, would be if the null hypothesis of no difference were true and the test assumptions held. Neither quantity conveys the probability that the null hypothesis is true, nor does either alone establish practical importance.

What does the sponsor analysis add?

The registry reports a linear regression analysis, with a mean difference in final values of 0.27 and p=0.021. This is the sponsor’s reported analysis, distinct from the unadjusted recalculation. The registry record does not report a confidence interval for this estimate or enough detail to determine why its estimate differs from the recalculated mean difference. The sponsor’s own analysis takes precedence when describing the trial’s reported result. The recalculation is useful as a transparent comparison of the posted group summaries, but it should not be treated as a replacement for the trial analysis.

The registry identifies the reported analysis as a superiority analysis. General statistical explanation: a superiority analysis tests whether the outcome in one group is greater or otherwise different in the prespecified direction than in the comparison group, according to the study’s analysis plan. The direction, model specification, covariates, and detailed testing procedure are not reported in the registry record. The label alone is not enough to reconstruct those details.

Why does the index matter?

The endpoint combines three communication practices into one score, with higher values representing more supportive communication. Combining items can offer a concise outcome, but it also means that the overall score does not show which individual practice accounted for any group difference. The registry reports Cronbach’s alpha=0.59. General statistical explanation: internal consistency describes how closely related the items are as a set; it is one aspect of measurement quality, not a complete assessment of validity or reliability. The registry record does not report item-level results or further measurement analyses.

The described endpoint is a two-week score, and the posted result is a final-value comparison. Although the outcome title uses the word “Change,” the available analysis description does not establish that the reported contrast is a change-from-baseline estimate. Details about baseline outcome measurement, covariate adjustment, missing-data handling, and the analysis population are not reported in the registry record. Those omissions limit the ability to reproduce or fully assess the reported model.

What can the analysis establish?

Random allocation can support a comparative interpretation when allocation, follow-up, measurement, and analysis are conducted appropriately. However, the registry record alone does not describe enough of these procedures to evaluate all assumptions. The endpoint is parent-reported, the number contributing to the outcome differs between groups, and the reported assessment is at one timepoint. The results therefore describe the posted outcome data and the registry analysis, with the stated uncertainty, rather than establishing a broad conclusion about all effects of the educational intervention.

10. Confidence Intervals and Precision

The unadjusted recalculated mean difference is 1.22 points, with a 95% confidence interval from 0.081 to 2.359. This interval expresses uncertainty in the estimated group difference under the assumptions of the recalculation. It does not mean that there is a 95% probability that the true difference lies within these particular endpoints. General statistical explanation: confidence-interval procedures are designed so that, over repeated studies conducted under the same assumptions, intervals constructed in this way would cover the underlying quantity at the stated rate.

The interval’s lower endpoint is positive but close to zero, while its upper endpoint allows for a larger difference. Thus the estimate is not equally precise across all plausible values: the posted data remain compatible with a range of magnitudes. Whether any part of that range represents a meaningful change cannot be determined from statistical precision alone. A threshold for a clinically or practically important score difference is not reported in the registry record.

The outcome summaries include 61 participants in Education as Usual and 14 in New Education. The smaller New Education group has a larger reported standard error, 0.540 compared with 0.215 for Education as Usual. General statistical explanation: unequal and limited group sizes can make estimates less precise, especially for the smaller group. The standard deviations, 1.68 and 2.02, also show that individual scores vary within both groups.

The registry’s linear regression estimate is 0.27 with p=0.021, but its confidence interval is not reported in the registry record. Its precision therefore cannot be evaluated from an interval in the posted analysis. The recalculated interval belongs to the unadjusted comparison and should not be assigned to the regression estimate.

11. Planning a Similar Trial: Sample Size

This is a planning illustration, not a re-evaluation of the original trial. It asks: if a new study wanted to detect a difference like the one observed, or a smaller one, how large would it need to be? It is deliberately not “observed power” of the finished trial, which is not a meaningful quantity.

The planning figures are participants per arm, not total events. They are illustrations based on the observed effect, not the trial’s own original design assumptions. The registry record does not report the original sample-size justification or its design assumptions.

The planning illustration assumes a two-sided significance level of 0.05, equal allocation between two arms, and a normal approximation. It considers effects at 100%, 75%, and 50% of the observed effect. The listed participant counts are given separately for planning for 80% power and planning for 90% power. In plain terms, the 80% column gives the estimated number of participants per arm under those assumptions for a design with an 80% chance of detecting the specified effect if it is present; the 90% column describes the corresponding target for a 90% chance.

For each power target, the planning requirement increases as the effect being targeted becomes smaller. A smaller separation between group averages is harder to distinguish from random variation, so more participants are needed under the same planning assumptions. The 100% row uses the full observed effect as the target; the 75% and 50% rows illustrate more conservative, smaller targets. These values are planning illustrations, not observed power. They do not indicate the probability that the completed study’s result is true or that the intervention has a particular effect.

The planning calculations are based on the recalculated observed effect and the stated assumptions. They should not be read as evidence that the trial was designed with those assumptions, nor as a reconstruction of its original protocol. The trial’s own design assumptions are not reported in the registry record.

12. How the Sample Size Is Derived

Power is the probability that a study of a given size rejects the null hypothesis when a specific true effect exists. It depends on four things: the effect to detect, the variability of the outcome, the significance level (here a two-sided α of 0.05, so z_1−α/2 = 1.960) and the desired power (z_1−β = 0.842 for 80% and 1.282 for 90%).

Formula

n is the number of participants in each arm, Δ is the difference in means to detect and σ is the common standard deviation.

Worked calculation for this trial

1. Observed difference Δ = 1.220; pooled standard deviation σ = 1.745.
2. n = 2 × (1.96 + 0.842)² × 1.745² / 1.220² = 32.1, rounded up to 33 participants per arm for 80% power.

The smaller-effect rows in the table above repeat the same calculation with the effect multiplied by 0.75 and 0.5 (for ratios, applied to the logarithm of the ratio).

R code

alpha <- 0.05
z_a   <- qnorm(1 - alpha / 2)          # two-sided
delta <- 1.22                      # observed difference in means
sigma <- 1.7454017867701                     # pooled standard deviation
n_per_arm <- function(power, frac = 1) {
  ceiling(round(2 * (z_a + qnorm(power))^2 * sigma^2 / (delta * frac)^2, 6))
}
for (f in c(1, 0.75, 0.5))
  cat(sprintf("%3.0f%% of observed effect: n per arm = %s (80%% power), %s (90%% power)\n", 100 * f,
              format(n_per_arm(0.80, f), big.mark = ","), format(n_per_arm(0.90, f), big.mark = ",")))

# Check against R's built-in function (t-based, so very slightly larger)
cat("power.t.test:", round(power.t.test(delta = delta, sd = sigma, power = 0.80)$n, 1), "\n")

# Simulation: exact two-sample t-test using simulated means and variances
set.seed(4112914)
n    <- n_per_arm(0.80)
reps <- 20000
m_diff <- rnorm(reps, delta, sigma * sqrt(2 / n))             # difference in sample means
s2     <- sigma^2 * rchisq(reps, 2 * (n - 1)) / (2 * (n - 1))   # pooled sample variance
tstat  <- m_diff / sqrt(s2 * 2 / n)
cat(sprintf("Simulated power at n = %s per arm: %.3f (%d replicates)\n", format(n, big.mark = ","), mean(abs(tstat) > qt(0.975, 2 * (n - 1))), reps))

Output from running the code

100% of observed effect: n per arm = 33 (80% power), 44 (90% power)
 75% of observed effect: n per arm = 58 (80% power), 77 (90% power)
 50% of observed effect: n per arm = 129 (80% power), 173 (90% power)
power.t.test: 33.1 
Simulated power at n = 33 per arm: 0.798 (20000 replicates)

The simulation draws many sets of group means and variances at the planned sample size and counts how often the two-sample t-test rejects the null. It should land close to the target power; at very small required sample sizes it can fall below it, because the normal approximation is rough there.

13. Analyses Reported by the Sponsor

The registry’s own analysis is a linear regression of final values, reporting a mean difference of 0.27 and p=0.021 for the two groups. The registry record does not provide a confidence interval for that estimate. The unadjusted recalculation from the posted group summaries gives a mean difference of 1.22, with a 95% confidence interval from 0.081 to 2.359 and p=0.036.

These are not identical estimates. The recalculation is a simple comparison of the reported means and does not reproduce the sponsor’s regression model. The registry record does not give enough detail about the model specification, covariates, or analysis population to explain the difference. There is no flagged discrepancy in the record, but that does not make the recalculation interchangeable with the sponsor analysis.

The sponsor’s own analysis takes precedence as the trial’s reported result. The recalculation can be read as a supplementary, unadjusted check on the posted summaries, with its own uncertainty, rather than as a correction or replacement for the reported regression result.

14. Multiplicity, Missing Data and Analysis Populations

The registry lists seven outcome measures and seven analyses. It identifies the communication behavior score as the primary outcome and names four secondary outcomes: changes in self-efficacy for communication, supportive or rehabilitation-related behaviors, and follow-up, and change in concussion knowledge. The available registry information does not show the results for those secondary outcomes.

When a study evaluates multiple outcomes or performs multiple statistical tests, the chance of obtaining at least one apparently notable result by chance can increase. General statistical explanation: multiplicity procedures can control or otherwise address this issue, depending on the study’s objectives and prespecified plan. Whether multiplicity was addressed, and how, is not reported in the registry record. The reported p-values should therefore be read as the analyses posted for the stated comparison, not as evidence that a particular multiplicity strategy was used.

Details about missing outcome data, reasons for nonresponse, imputation, and sensitivity analyses are not reported in the registry record. The primary outcome summaries include 61 participants in Education as Usual and 14 in New Education, while enrollment is listed as 98. The record does not explain the difference between enrollment and the number with posted primary outcome data. The extent to which missingness could affect the estimates cannot be assessed from the reported information.

The analysis population is not described in sufficient detail to determine whether the reported comparison followed an intention-to-treat approach or another population definition. The registry record also does not report a full statistical analysis plan, baseline balance information, covariate choices, or the handling of protocol deviations. These details matter for evaluating how the analysis was selected and whether the reported groups and estimates correspond to the randomized comparison.

15. Safety Results

The registry reports serious adverse events as affected participants divided by participants at risk.

Deaths

Other (non-serious) adverse events

Participants with at least one non-serious event at or above the registry's 0% reporting threshold.

The registry lists serious adverse events and other adverse events separately for the two groups. For Education as Usual, 75 participants were listed as at risk; there were 0 serious adverse events, 0 other adverse events, and 0 deaths. For New Education, 23 participants were listed as at risk; there were 0 serious adverse events, 0 other adverse events, and 0 deaths.

These figures describe the adverse-event counts recorded in the registry. They do not by themselves establish that no adverse events occurred outside the reported observation or reporting procedures. The registry record does not provide further details about event definitions, duration of safety follow-up, collection methods, or whether the at-risk populations match the primary outcome populations. With no events recorded in these groups, the registry provides no event-level information for comparing types or timing of adverse events.

Safety counts should be interpreted separately from the parent-reported communication outcome. The absence of recorded events does not establish the absence of risk, and these figures do not determine whether the educational intervention is beneficial or appropriate for any individual family.

16. What the Result Does, and Does Not, Mean

The posted primary outcome data show a higher mean parent-reported communication score in the New Education group than in the Education as Usual group at two weeks. The unadjusted recalculation estimates a mean difference of 1.22 points, with a 95% confidence interval from 0.081 to 2.359 and p=0.036. The registry’s regression analysis reports a mean difference of 0.27 and p=0.021. The two estimates arise from different analyses, and the registry does not report enough detail to reconcile them.

The score represents three parent-reported communication practices and ranges from 3 to 9, with higher scores indicating more supportive communication. The results therefore concern this measured aspect of family communication, not all communication, the child’s health status, or adherence to return-to-activity guidance. The registry record does not report a threshold for interpreting the size of a score difference as important to families or clinicians.

The evaluation was described as hybrid implementation-effectiveness research, but the primary result alone does not establish whether the intervention was successfully implemented or whether implementation improved knowledge, self-efficacy, or health-literacy disparities. Although those topics appear in the study description and outcome list, the relevant results are not reported in the registry record.

The findings are based on parent self-report at a single stated post-visit timepoint. The posted summaries do not establish a baseline change, longer-term persistence, or independent confirmation of the reported behaviors. The unequal numbers contributing to the group summaries and the limited information about missing data also constrain interpretation. Statistical evidence in this comparison should not be treated as proof of causation, clinical importance, or benefit for every family.

17. Why This Trial Matters Statistically

This study asks a practical measurement question: whether an educational approach in the emergency department is associated with parent-reported communication behaviors at home after a child’s concussion visit. The endpoint connects the setting of care with a specific behavior during recovery, rather than relying only on a general satisfaction measure or a broad knowledge score.

Statistically, the record illustrates why the analysis method and the estimate must be read together. The simple unadjusted recalculation from group means produces a different mean difference from the registry’s linear regression analysis. Without the model details, the two values cannot be reconciled confidently. Reporting the analysis method, population, adjustment strategy, and confidence interval would help readers evaluate the result and understand the source of uncertainty.

The record also emphasizes the distinction between statistical evidence and practical importance. The recalculated interval indicates a range of compatible differences, but the registry does not report a meaningful-change threshold for the communication index. The scale’s reported Cronbach’s alpha=0.59 is another reason to consider measurement properties when interpreting a composite outcome: a score can be useful while still requiring caution about how consistently its component items behave.

Finally, the study description includes implementation, knowledge, self-efficacy, and disparity questions, while the posted primary result addresses one self-reported behavior outcome. Keeping those questions separate prevents a result on one endpoint from being extended to outcomes that are not reported.

18. Limitations

• The posted summary statistics are the only data these results rest on; patient-level data, full protocols and statistical analysis plans are not available.
• Recalculated results are simple, unadjusted calculations from posted summaries. They do not replace the sponsor's prespecified analysis.

The primary endpoint is based on parent self-report, which may not correspond exactly to observed communication. It combines three practices into a single index, so the reported overall score does not reveal which specific practice contributed to the group difference. The registry reports Cronbach’s alpha=0.59, and does not provide item-level results or further measurement analyses.

The available primary summaries include 61 participants in Education as Usual and 14 in New Education, while the recorded enrollment is 98. The registry record does not explain the numbers contributing to the outcome, describe reasons for missing data, or report how missingness was handled. This makes it difficult to assess whether the observed participants represent the enrolled groups.

The outcome is described as a change, but the posted summaries and the reported regression concern final values at the two-week timepoint. A baseline-adjusted change estimate is not reported in the registry record. The sponsor’s regression estimate is 0.27, whereas the unadjusted recalculation is 1.22; the model details needed to explain their difference are not reported. The sponsor analysis has no posted confidence interval.

The record identifies randomization but does not give further details about allocation procedures, the sequential model, the analysis population, or the study’s original sample-size justification. It lists several outcomes, but multiplicity handling and results for the named secondary outcomes are not reported in the registry record. These limitations narrow what can be concluded from the primary comparison.

19. Related Tutorials

20. Related Statistical Calculators

21. Sources

• ClinicalTrials.gov: Developing an Implementation Strategy for Post-concussion Communication With Low Health Literacy Parents in the Emergency Department — NCT04112914.
• Registry record last updated 2024-04-29; status last verified 2024-04.
• Results first posted 2024-04-29.
• Data retrieved from ClinicalTrials.gov on 2026-11-09.
• Group sizes, means, event counts and sponsor-reported p-values are reproduced as posted. Effect estimates, confidence intervals and p-values not attributed to the sponsor are independently calculated from the posted summary statistics.

22. Record Summary

NCT04112914 is a completed randomized, unmasked study sponsored by Seattle Children’s Hospital. It evaluated a newly developed post-concussion education intervention against education as usual during an emergency-department visit. Enrollment was 98, and the recorded study dates were 2021-01-05 for start and 2022-07-27 for primary completion.

The primary outcome was parent-reported supportive communication behavior two weeks after the visit, measured with a three-item score ranging from 3 to 9. The registry reports group means of 5.49 for Education as Usual and 6.71 for New Education. Its linear regression analysis reports a mean difference of 0.27 and p=0.021. An unadjusted recalculation gives a mean difference of 1.22, with a 95% confidence interval from 0.081 to 2.359 and p=0.036.

Details about missing data, multiplicity, the original design assumptions, and the regression specification are not reported in the registry record. No serious adverse events, other adverse events, or deaths were recorded in either group.